Ionospheric Sounding Using GNSS-RO - GNSS Remote Sensing: Theory, Methods and Applications - page 166

Fig. 7.4 a view of recursive scheme of the Abel inversion

Obviously, each TEC observation can determine a layer in the vertical profile.
Further, the sampling rate of receivers equipped on the LEO satellites determines
the vertical resolution of the profile.

n

X

1

TEC.n/ 2￿ Ne .a i / ￿l i;n

i D1

Ne .a n / D (7.18)

2￿l n;n

Using Eq. ( 7.18 ), the electron density can be obtained layer by layer from the
uppermost observation to the lowermost observation.

7.2.4 Amplitude Inversion

GNSS-RO observations contain not only phase observations but also amplitude
variation information. Although the precision of bending angle derived from
amplitude measurement is not as good as phase measurement, but it is applied
in GNSS-RO physical inversion, such as back propagation algorithm (Gorbunov
et al. 2000 ) and diffraction method (Melbourne et al. 1994 ). The variation of the
amplitude is mainly caused by focusing or defocusing as well as associating with
the atmosphere absorption and scattering effect. It may play an important role in
optimizing phase inversion, monitoring multipath propagation, finding anomalies